SK Telecom Waves the Flag for Its 5G Trial

The South Korean government has a lot at stake for the Winter Olympics 2018. Not only is it hoping to host a vibrant and successful Olympic experience, but it also wants to show the world a fully operational 5G network. The Olympics are only 18 months away. During Mobile World Congress (MWC) Shanghai, SK Telecom, with support from Nokia and Samsung, declared it had tested an end-to-end infrastructure trial of a 5G network. There are a number of distinctive features that could pinpoint the underlying technologies and network strategies advanced mobile telcos will deploy for 5G. 

• SK Telecom stated it intends to use 3.5 GHz for “wider area coverage,” and 28 GHz for downtown city environments, where it will provide ultra-fast broadband connections. The 3.5 GHz band is not just for low-density urban environments and villages, but also for communicating with autonomous/connected vehicles. Transmissions over 10 GHz are likely be TDD, while FDD will be the configuration for the sub-3 GHz band. In the 3 GHz band to 10 GHz band, either FDD or TDD could be used.
• SK Telecom’s 5G NR basestations will be transceiving with a subcarrier spacing of 60 KHz, and a Transmit Time Interval (TTI) length of 0.25 ms. This implementation will help the mobile telco to reduce latency to the ITU 2020 target goal of <10 ms. Achieving sub-10 ms latency is essential for autonomous driving support, as well as for smart manufacturing applications. Attaining these latency levels is also supported by a sub-frame structure that simultaneously supports downlink data and uplink feedback.  
• In order to boost data throughput speeds, the 5G NR channel coding supports Low-Density Parity-Check (LDPC). LDPC is a linear error correcting code that is effective transmitting data over a noisy transmission channel. LDPC is used in conjunction with OFDMA.
• The above technical strategies will complement OFDM, or Orthogonal Frequency-Division Multiplexing. OFDM will still be at the center of 5G NR, as it was at the heart of the 4G LTE networks. OFDM has a number of features that still admirably suit it to a next-generation network such as 5G. OFDM is one of the most spectrally efficient schemes around, is MIMO-compatible, resistant to channel time, with excellent channel frequency and selectivity. 

SK Telecom believes these 5G NR enhancements will help the operator to roll out not just autonomous/connected vehicular services, but also critical machine-type communications, as well as Internet of Things (IoT), augmented reality (AR), and virtual reality (AR) applications.

It is a promising sign to see mobile telcos and infrastructure vendors such as Nokia and Samsung prototyping and testing 5G infrastructure solutions. Of course, there is still a substantial amount of manufacturing process R&D to complete. 5G NR will no doubt find its way into a number of spectrum bands. The Korean regulatory authorities are expected to issue the long-term 5G spectrum licenses after the 5G Olympic trial licenses expire. The Japanese and the Chinese have expressed interest in the 4.x GHz band. Other microwave/millimeter bands have also been mooted, such as 35 to 39 GHz and even higher. The sub-3 GHz will be tricky in the short term. Fundamentally, existing stakeholders have to be vacated (or incentivized to move on), or use refarmed mobile cellular spectrum.

The only other 5G component missing is the 5G handset. That should be ready (or some form of it) by March 2018; at MWC Barcelona 2017, Samsung promised it would have a working 5G NR smartphone ready by that date. The clock is ticking.